I've bought this board recently. I suppose it's Soyo SY-020C, it looks just so, will tell definitely when it arrives.

I have a question about proprietary memory connector - have somebody seen such expansion boards? Is it something like SIMM30 to SIMM72 with 8-16 additional simm sockets on it or some board with chips soldered on top? Any pinouts?

Hope it works 😀 I have to remove the battery, clean and probably restore all corroded places but then it would be interesting to play with memory slot.